RADPx-OS exposes one stable C ABI through radkernel.h. The smaller subsystem headers, such as rad_vfs.h and rad_spi.h, include that ABI and exist so drivers and applications can include the subsystem they use.

Initialization And Boot

Platform code fills rad_boot_info_t when firmware or a bootloader has already provided memory maps, command-line arguments, an initrd pointer, or an FDT pointer. The kernel is then initialized with rad_kernel_init() and driven by rad_kernel_poll() or rad_kernel_run().

Use rad_printk() for normal kernel logging and rad_early_printk() before the regular console path is registered.

Runtime Services

The core runtime is intentionally explicit:

Tasks, wait queues, timers, mutexes, and events provide RTOS-style in-kernel concurrency primitives.
Process, syscall, file descriptor, and VFS APIs provide the POSIX-inspired userspace path.
Device, block, network, framebuffer, input, TTY, PTY, serial, audio, I2C, SPI, DMA, IRQ, and module APIs are the driver-facing kernel boundary.
The overlay tree binds platform description to buses, child devices, framebuffers, and interrupt domains.

Platform Layout

Architecture and SoC code is split under RADKernel/platforms. Portable A53 execution code belongs in platforms/a53; Broadcom-specific Pi drivers belong under platforms/a53/bcm283x. The x86 VM target remains the parity reference and will move under platforms/x86 once its target wrapper is thin enough to avoid behavior changes.

Handle Rules

Opaque handles are owned by the caller after a successful open/create call. Close or destroy them with the matching close/destroy function. Functions return RAD_STATUS_OK on success, a negative rad_status_t value on kernel API errors, or a negative POSIX-style result for file descriptor/syscall wrappers.

Crimson Stability

Crimson 0.1.4 documents the intended public shape for beta work. APIs marked as experimental may change before the stable release; APIs marked stable-beta should keep source compatibility inside the Crimson branch unless a documented release note says otherwise.